Applications of automated simultaneous double fluorescence (SDF): I. Unbiased, quantitative HLA-A,B phenotyping

Gluten sensitivity in monozygous twins: a long-term follow-up of five pairs

OBJECTIVE

The aim of this study was to investigate the role of genetic factors and the characteristics of five monozygous twin pairs with at least one member affected by gluten sensitivity.

METHODS

Five pairs of monozygous female twins, of whom one or both were affected by gluten sensitivity (i.e., celiac disease or dermatitis herpetiformis), were followed-up for 11-23 yr.

RESULTS

Three pairs were concordant for celiac disease: the onset was comparable and synchronous in two pairs; in the third, one member presented an overt malabsorption syndrome, and the other developed iron deficiency anemia 10 yr later. Discordance for gluten sensitivity was found in the remaining two pairs, one of whose members was diagnosed as having, respectively, celiac disease and dermatitis herpetiformis.

CONCLUSIONS

As no environmental factors were found to affect the phenotypic expression of the disease, genetic factors seem to play a major role. The presence of overt or latent celiac disease in three of the four siblings of the three concordant twins, and the association with cystic fibrosis in all three siblings of one of these families, further supports this hypothesis.

High frequency of T-cell lines responsive to immunodominant epitopes of thyrotropin receptor in healthy subjects

In this study we analyzed the proliferative response to the extracellular domain of thyrotropin receptor (TSHR-ECD) of T-cell lines raised from healthy subjects. We found high frequencies of cell lines reactive to TSHR-ECD, ranging from 12% to 37%. The response of the cell lines to a set of overlapping peptides of TSHR-ECD showed that the most recognized epitopes by T lymphocytes are on the C-terminal portion. In particular, the regions of residues 360-396 and 258-277 are immunodominant in T-lymphocyte reactivity. A group of cell lines specific for the peptides of TSHR-ECD lost the response to the peptides during time in culture. However, these lines were still responsive to TSHR extracellular domain. The cloning of one of these lines showed three types of T-cell clones: (1) CD4+ clones (n = 4) highly responsive to the TSHR-ECD; (2) CD4+ clones (n = 4) low responsive to TSHR-ECD; (3) CD8+ clones (n = 9) not responsive to TSHR-ECD. The first group of clones was stable during time in culture, while the second group was characterized by the loss of the specific response to TSHR-ECD after some weeks from the first analysis. The observation of a spontaneous anergy in the second group of CD4+ clones suggests that mechanisms of control of the lymphocyte response to TSHR-ECD could be activated in vitro.

Applications of automated simultaneous double fluorescence (SDF). II. HLA class I phenotyping using immunomagnetically separated T lymphocytes

HLA class I phenotyping was performed using T-lymphocyte populations isolated by immunomagnetic beads (IMBs) coated with monoclonal antibodies with specificity for CD2, CD4 or CD8. The results were compared to those obtained using density gradient-separated lymphocytes (PBL). The typing trays were read by the automated simultaneous double-fluorescence (SDF) technique previously established in our laboratory using an Astroscan 2100 system. The aims of the present study were to establish whether the advantages of IMB lymphocyte separation and automated plate reading by SDF were complementary and whether the results obtained by IMB-SDF and PBL-SDF were concordant. Similarity coefficients for paired results obtained by IMB-SDF and PBL-SDF varied between 0.825 using anti-CD8-coated IMBs and 0.914 using anti-CD4-coated IMBs with a consistent excess of stronger results observed with the PBL-SDF technique. The variations observed did not result in incorrect phenotype assignment but would significantly influence a cross-matching test. These results illustrate the feasibility of using IMB-separated lymphocytes for HLA phenotyping by SDF.